1. Field of the Invention
This invention relates to an integrated radiation image recording and read-out apparatus comprising a image recording section for exposing a stimulable phosphor sheet to a radiation passing through an object to have a radiation image of the object stored thereon, an image read-out section for exposing the stimulable phosphor sheet to stimulating rays which cause them to emit light in proportion to the stored radiation energy, and detecting and converting the emitted light into electric signals which are used to reproduce a visible image from the read-out image information, and an erasing section for releasing the radiation energy remaining on said stimulable phosphor sheet after read-out. This invention particularly relates to such an apparatus in which stimulable phosphor sheets are circulated and reused for recording images and more particularly to such an apparatus in which a plurality of different types of stimulable phosphor sheets are circulated and reused for recording images.
2. Description of the Prior Art
When certain kinds of phosphors are exposed to a radiation such as X-rays, .alpha.-rays, .beta.-rays, .gamma.-rays, cathode rays or ultraviolet rays, they store a part of the energy of the radiation. Then, when the phosphor which has been exposed to the radiation is exposed to stimulating rays such as visible light, light is emitted from the phosphor in proportion to the stored energy of the radiation. A phosphor exhibiting such properties is referred to as a stimulable phosphor.
As disclosed for example in Japanese Unexamined Patent Publication No. 56(1981)-11395 and U.S. Pat. Nos. 4,258,264, 4,315,318, 4,387,428 and 4,276,473, it has been proposed to use a stimulable phosphor in a radiation image recording and reproducing system. Specifically, a sheet comprising the stimulable phosphor (hereinafter referred to as a stimulable phosphor sheet) is first exposed to a radiation passing through an object such as a part of the human body to have a radiation image stored thereon, and then is scanned with stimulating rays which cause it to emit light in proportion to the radiation energy stored. The light emitted from the stimulable phosphor sheet when the sheet is exposed to the stimulating rays is photoelectrically detected and converted to an electric image signal, which is processed so as to reproduce a visible image having an improved quality, particularly a high diagnostic efficiency and accuracy. The finally obtained visible image may be reproduced in the form of a hard copy or may be displayed on a cathode ray tube (CRT). In this radiation image recording and reproducing system, the stimulable phosphor sheet is used only for temporarily storing the radiation image in order to reproduce the final visible image therefrom in a final recording medium. For economical reasons, therefore, it is desirable that the stimulable phosphor sheet be used repeatedly.
Further, in a mobile X-ray diagnostic station such as a traveling X-ray diagnostic station in the form of a vehicle like a bus which is provided with a radiation image recording and read-out apparatus for use in the aforesaid radiation image radiation recording and reproducing system and moves from place to place to record radiation images for mass medical examinations, it is disadvantageous to load the mobile X-ray diagnostic station with a large number of stimulable phosphor sheets, and the number of stimulable phosphor sheets loaded on the mobile X-ray diagnostic station should be minimized. Therefore, it is desirable to load the mobile X-ray diagnostic station with stimulable phosphor sheets which can be used repeatedly, once store the radiation images of the objects on the stimulable phosphor sheets, transfer the electric image signals read out from the stimulable phosphor sheets onto a recording medium having a large storage capacity, such as a magnetic tape, and circulate and reuse the stimulable phosphor sheets for further image recording and read-out operations, thereby to obtain the radiation image signals of many objects. Further, when image recording is conducted continuously by circulating and reusing the stimulable phosphor sheets, it becomes possible to increase the image recording speed in mass medical examinations. This is very advantageous in practical use.
In order to reuse stimulable phosphor sheets as described above, the radiation energy remaining on the stimulable phosphor sheet after it is scanned with stimulating rays to read out the radiation image stored thereon should be eliminated or erased as described, for example, in Japanese Unexamined Patent Publication No. 56(1981)-12599 and U.S. Pat. No. 4,470,619. The stimulable phosphor sheet can then be used again for radiation image recording.
From the practical point of view, therefore, it is very convenient to use an integrated apparatus in which at least one stimulable phosphor sheet is reused by repeatedly circulating it through an image recording section for recording a radiation transmission image of an object on the stimulable phosphor sheet by exposing it to a radiation passing through the object, an image read-out section for reading-out the radiation image stored on the stimulable phosphor sheet in the image recording section, and an erasing section for releasing the radiation energy remaining on the stimulable phosphor sheet after read-out so as to prepare it for recording of the next image thereon. This is because such an integrated apparatus can be easily installed in a mobile X-ray diagnostic station, thus making it easier to move from place to place for mass examinations, or in a hospital or the like.
The applicant therefore proposed in U.S. patent application No. 600,689 an integrated radiation image recording and read-out apparatus comprising an image recording section, an image read-out section and an erasing section built into a single unit further provided with a circulation and conveyance system for enabling circulation and reuse of the stimulable phosphor sheets.
Although this integrated apparatus is very convenient in actual practice since it makes it possible to continuously carry out the recording, read-out and erasure of radiation image information by repeatedly circulating one or more stimulable phosphor sheets, it has the shortcoming of being difficult to use with a plurality of different types of stimulable phosphor sheets. More specifically, when a plurality of different types of stimulable phosphor sheets are circulated through the appatatus, it is not easy to carry out recording and read-out of radiation image information using a selected one of the different types of sheets whenever the need arises.
This shortcoming of the apparatus becomes an especially serious problem when the apparatus is used for recording and read-out of radiation images of different types of objects such as the chest, head, bone and stomach of human beings, since in such cases it is general practice to select from among a plurality of different types of stimulable phosphor sheets the particular type that is best suited as regards sharpness, sensitivity etc. With the integrated apparatus, although it is possible to circulate a plurality of different types of stimulable phosphor sheets, after these sheets have been started circulating it is very difficult to change the order in which they circulate, so that in the image recording operation when the stimulable phosphor sheet that happens to be at the image recording section is of a different type from the desired one, the operator can only keep sending the stimulable phosphor sheets through the image recording section without recording images thereon until a stimulable phosphor sheet of the desired type arrives at the recording section. In the actual recording and read-out of radiation images this is inconvenient and also considerably impairs the efficiency of the recording and read-out operations.